The present invention relates to the laser processing of a glass by laser light irradiation. More particularly, the invention relates to a glass composition suitable for laser processing.
Members obtained through the microprocessing of a glass base, such as optical parts for use in optical communication and microlenses to be mounted in displays, are used in a wide range of fields. This microprocessing of a glass base has generally been conducted by wet etching (chemical etching) with an etchant such as, e.g., hydrofluoric acid or dry etching (physical etching) such as, e.g., reactive ion etching.
However, the wet etching has problems concerning the compositional regulation of etchants and the treatment of waste liquids. The dry etching has problems that a vacuum apparatus or the like is necessary and that the processing is not efficient because of the necessity of complicated steps, e.g., the step of forming a pattern mask by photolithography.
On the other hand, the technique of direct processing is progressing in which a laser light is caused to strike on a work to cause a physical change such as heating, melting, vaporization, or ablation and this change is used to process the work. Since a laser light can be focused to an extremely small spot, it is suitable for use in microprocessing. This is a completely physical processing technique and is hence free from the problems accompanying the wet etching. Furthermore, since this laser light processing can be conducted in air with laser light scanning, it is also free from the problems accompanying the dry etching heretofore in use.
With the progress of laser technology, reductions in laser pulse duration and reductions in wavelength have realized and it has become possible to process organic materials, e.g., polyamides, and metals on the order of micrometer. However, since glasses are brittle materials, they are apt to crack during processing. It has hence been not easy to use a laser light for the microprocessing of glass materials.
For example, Japanese Patent Laid-Open No. 217237/1999 discloses, for eliminating those problems, a technique for providing a glass less apt to crack by incorporating silver into a glass by ion exchange and thereby reducing the threshold value for laser processing.
However, in most glasses containing alkali metals, the following phenomenon occurs. Although silver ions can be incorporated into the glass through silver ion exchange, the silver ions are reduced in an area near the glass surface and the diffusion of silver ions into inner parts of the glass is thus inhibited. Because of this, the effective region for laser processing is limited to the area near the glass surface and it is hence still difficult to conduct processing of the glass up to an inner part thereof, e.g., formation of a through-hole in the glass plate. There has also been a problem that the rate of ion exchange is low and it is difficult to cause ions to stably reach inner parts of the glass.
An aim of the invention is to provide, in order to eliminate the problems described above, a glass for laser processing which contains an element capable of being incorporated not through ion exchange but at the time of glass melting and serving to lower the threshold value for processing.